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Research has been conducted on the selective reduction of alkynes to alkenes. Results demonstrate that the use of indium in aqueous ethanol provides a highly selective reduction of the terminal alkynes to alkenes in aryl propargyl ethers, amines and esters.

A new approach for the synthesis of tetrasubstituted/functionalized NH-pyrroles from gem-diactivated acrylonitriles and TMSCN has been developed. The strategy utilizes the generation of vic-dinitrile via Michael addition and cyanide-mediated nitrile-to-nitrile cyclocondensation, which proceed in tandem guided by manifold roles of "CN". An extended application to the production of fused pyrrole has also been realized. [ABSTRACT FROM AUTHOR]

A step-economical access to polysubstituted aminoimidazoles has been accomplished via alkene vicinal C-N bonds formation of 2-bromo-2-alkenones with guanidine avoiding its NH-protection/derivatization prerequisite for electronic modulation. The approach has excellent substrate scope, is amenable to diverse guanidine-containing substrates, and introduces distinctive substitutions/functionalities into aminoimidazole core. It is also applicable to preparation of fused-imidazoles. The reaction involves a tandem pathway of aza-Michael addition, SN2, and a unique redox-neutral process, as evident by spectroscopic study and control experiments. [ABSTRACT FROM AUTHOR]

A study was conducted to determine the applicability of ammonium formate/Pd-C in reducing the C=C bond in alpha,beta-unsaturated sulfones and phosphonates. The results showed that the substituents on the aromatic ring do not affect the process of hydrogenation. The method led to high yields of products at mild reaction conditions. It is also operationally simple and the reagents are easily available and relatively cheaper.

A regioselective Ag(I)-promoted Pd-catalyzed C3-H activation-arylation of pyrido[1,2-a]pyrimidin-4-ones with bromo/iodo-(hetero)arenes under aqueous conditions has been developed. It affords an efficient access to pharmaceutically important versatile 3-aryl-pyrido[1,2-a]pyrimidin-4-ones. Interestingly, the arylation undergoes via a pathway with an unusual feature involving the formation of cationic arylpalladium species promoted by halo-sequestering Ag salts enabling concerted C3-palladation-deprotonation, as explored by relevant experiments and spectroscopic studies. The present approach is step economical, good yielding, and compatible with various functionalities and applicable to a wide range of starting materials. [ABSTRACT FROM AUTHOR]

A new and efficient approach for the synthesis of biologically important 2-aryl-4H-pyrido[1,2-a]pyrimidin-4-ones and 6-aryluracils via previously unknown Pd-catalyzed enolic C-OH activation-arylation of pyridopyrimidin-2,4-diones and barbituric acids, respectively, with boronic acids is reported. The starting materials are readily available, and products are obtained in high yields. An efficient and chemo- and stereoselective access to various tri- and tetrasubstituted conjugated alkenones and alkenoates is also obtained in this arylation approach. Interestingly, the procedure for the construction of such diverse molecular frameworks is general and featured with excellent substrates scope, tolerance of a broad range of functionalities, the unusual viability of performing the reaction under open air and in aqueous cosolvent, and the amenability to a scale-up synthesis, which have been found to be common limitations in the conventional/classical routes. The application of the protocol in a simple one-step high-yield route to pharmaceutically important polyarylated pyridopyrimidinone demonstrates its further synthetic utility. [ABSTRACT FROM AUTHOR]

Concerted metalation deprotonation (CMD) approach with appropriate proton shuttle precursor, base, and solvent (PivOH--K2CO3--toluene) has rendered a regioselective Pd-catalyzed C6-arylation of 3-aminoimidazo[1,2-a]pyrazine, a therapeutically relevant scaffold accessible by multicomponent reaction. The arylation of this heteroarene suffers from competing C5 and C2'-arylation reactions, while the developed process has virtually eliminated these competing arylanons. Density functional calculations for CMD C-H activation at C6, C5, C8, and C2' sites imply that the energy barrier with distortion energy penalty as major contributing component influences the regioselectivity. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of mixed Cu(I)-Cu(II) system in situ generated by partial reduction of CuSO4 with glucose in ethanol (nonanhydrous) under open air has been explored. With this catalysis, the multicomponent cascade reaction of A³-coupling of heterocyclic amidine with aldehyde and alkyne, 5-exo-dig cycloisomerization, and prototropic shift has afforded an efficient and eco-friendly synthesis of therapeutically important versatile N-fused imidazoles. Diverse heterocyclic amidines, several of which are known to be poorly reactive, and aldehydes are compatible in this catalytic process. [ABSTRACT FROM AUTHOR]

An efficient method for regio- and chemoselective Friedel-Crafts acylation of indole using acyl chlorides in the presence of ZrCl4 has been discovered. It minimizes/eliminates common competing reactions that occur due to high and multiatom-nucleophilic character of indole. In this method, a wide range of aroyl, heteroaroyl alkenoyl, and alkanoyl chlorides undergo smooth acylation with various indoles without NH protection and afford 3-acylindoles in good to high yields. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of mixed Cu(I)-Cu(II) system in situ generated by partial reduction of CuSO(4) with glucose in ethanol (nonanhydrous) under open air has been explored. With this catalysis, the multicomponent cascade reaction of A(3)-coupling of heterocyclic amidine with aldehyde and alkyne, 5-exo-dig cycloisomerization, and prototropic shift has afforded an efficient and eco-friendly synthesis of therapeutically important versatile N-fused imidazoles. Diverse heterocyclic amidines, several of which are known to be poorly reactive, and aldehydes are compatible in this catalytic process.

An efficient method for regio- and chemoselective Friedel-Crafts acylation of indole using acyl chlorides in the presence of ZrCl(4) has been discovered. It minimizes/eliminates common competing reactions that occur due to high and multiatom-nucleophilic character of indole. In this method, a wide range of aroyl, heteroaroyl alkenoyl, and alkanoyl chlorides undergo smooth acylation with various indoles without NH protection and afford 3-acylindoles in good to high yields.